The present invention is directed to a diverter tool for diverting fluid from a work string to the annular space around the work string and more specifically is directed to a diverter that can be used during drilling operations and will divert fluid into an annular space as the fluid in the drill string is moving toward the drill bit.
In the construction of oil and gas wells, a wellbore is drilled into one or more subterranean formations or zones containing oil and/or gas to be produced. The wellbore is typically drilled utilizing a drilling rig which has a rotary table on its floor to rotate a pipe string during drilling and other operations. During a wellbore drilling operation, drilling fluid (also called drilling mud) is circulated through a wellbore by pumping it down through the drill string, through a drill bit connected thereto and upwardly back to the surface through the annulus between the wellbore wall and the drill string. The circulation of the drilling fluid functions to lubricate the drill bit, remove cuttings from the wellbore as they are produced and exert hydrostatic pressure on the pressurized fluid containing formations penetrated by the wellbore to prevent blowouts.
In most instances, after the wellbore is drilled, the drill string is removed and a casing string is run into the wellbore while maintaining sufficient drilling fluid in the wellbore to prevent blowouts. The term “casing string,” or casing is used herein to mean any string of pipe which is lowered into and cemented in a wellbore including but not limited to surface casing, liners and the like. As is known in the art, the term “liner” simply refers to a casing string having a smaller outer diameter than the inner diameter of a casing that has already been cemented into a portion of a wellbore.
A wellbore may have more than one casing or liner cemented therein. For example, a wellbore may have a casing cemented therein, and a first liner cemented therein below the casing. In some cases, it may be desirable to drill below the first liner, and cement a second liner in the well below the first liner. The wellbore below the first liner may be drilled with a drill bit, or other cutting apparatus attached to the second liner.
The second liner will be lowered into the well with a drill string, which in most cases will have an outer diameter smaller than the outer diameter of the second liner. Drilling fluid will be displaced through the drill string, the second liner, and the cutting apparatus, and will travel up the annulus between the second liner and the wellbore, and into the annulus between the first liner and the second liner. The drilling mud will pass into and upwardly to the annulus between the drill string and the first liner, and the drill string and the casing.
The drilling mud is used to remove drill cuttings and solids by carrying the drill cuttings and solids upwardly to the surface. The size of the annulus or space between the casing and the drill string is greater than the size of the annular space between the first liner and the second liner, and the size of the annulus between the drill string and the first liner is greater than the annulus between the first liner and the second liner. The rate of flow of drilling fluid, in many cases, may not be sufficient to ensure that the drill cuttings and solids are removed from the annular space between the casing and the drill string and/or the drill string and first liner. Thus, there is a need for an apparatus and method that will ensure adequate solids removal in such circumstances.